[gmx-users] Adapting metallic ions from AMBER to GROMACS

Pedro Lacerda pslacerda+gmx at gmail.com
Wed Apr 20 00:24:31 CEST 2016


Very thanks,

I'm trying it right now.

Pedro Lacerda

2016-04-18 21:29 GMT-03:00 Mark Abraham <mark.j.abraham at gmail.com>:

> Hi,
>
> Convert the units and absorb the factor of two to the minus six. Compare
> with other ions present in both representations of such force fields.
>
> Mark
>
> On Tue, 19 Apr 2016 02:21 Pedro Lacerda <pslacerda+gmx at gmail.com> wrote:
>
> > Hi Gromacs users,
> >
> > We are planning a simulation with a metallic (fe+2) attached on the
> > protein. The parameters found in [1] cannot be directly inserted on
> > ffnonbonded.itp because equation 1 of [1] and equation 4.5 of [2] are
> > slightly different.
> >
> > Theoreticaly these Lennard-Jones parameters could be used in any PME
> based
> > force field, but it was derived and tested using the AMBER software and
> > potential, so it is our current force field of choice. In
> > amber99sb-ildn/ffnonbonded.itp the long range interactions are described
> in
> > terms of epsilon (kJ/mol) and sigma (Rmin; nm).
> >
> > Eq 1:
> >
> >     Lj = 4e ((R/r)^12 - (R/r)^6)
> >
> > Eq 4.5:
> >
> >     Lj = e ((R/r)^12 - 2(R/r)^6)
> >
> > Seems that Rmin values are written as Rmin/2 in AMBER files avoiding some
> > calculations to optimize the software. But this occurs at implementation
> > level and probably does not have correspondence with the paper.
> >
> > My question is how can I adapt these parameters so they can be used in
> > Gromacs?
> >
> > (Sorry about the previous email, now the title is correct)
> >
> > [1]
> > http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3728907/pdf/nihms481931.pdf
> >
> > [2] ftp://ftp.gromacs.org/pub/manual/manual-5.1.2.pdf
> >
> > [3] http://comments.gmane.org/gmane.science.biology.gromacs.user/82242
> >
> >
> > Cheers,
> >
> > Pedro Lacerda
> > --
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